This will generally work okay provided that the water heater give enough BTU.
Because the radiant heating water and domestic hot water are commingled, it is possible to turn on the faucet and get only lukewarm water if the space heating part of the system just kicked on and the floors were quite cool, pulling down the temperature of the entire "body of water".
Is this considered a "normal" installation? Given all the pipework as shown, how hard would it be to extricate the water heater and replace when it springs a leak? Also the warranty may be voided by this usage.
When cleaning anything including baby diapers, it is better to sweep off or scrape off as much solid and semisolid material as you can first. (1) Less cleaning fluid or detergent needs to be used, (2) Less of a mushy mess which in turn means that bleaches or disinfectants will be more effective.